Week 3 Find percentages and fractions of amounts

Week 3 Find percentages and fractions of amounts

Find percentages and fractions of amounts

• Bronze: Calculate a percentage of an amount

• Silver: Calculate a fraction of an amount

• Gold: Use reasoning skills to compare fractions and percentages.

Percentages without a calculator

• To find a percentage of an amount we do the same calculation to the amount as we would do to get from 100% to our percentage.

• To get from 100% to 1% we would need to divide by 100, so we would divide the amount by 100.

• We always use multiply or divide.

Percentages without a calculator

Multiple Choice

What sum would we do to find 60%?

• $$\div10\times6$$

• $$\div60$$
  

• $$\div6\times10$$

What sum would we do to find 60%?

• As 60 is a multiple of 10, we can find 10% then multiply it by 6 to get 60%

Fill in the Blanks

What sum would we do to find 75%

Use / for to show divide.

What sum would we do to find 75%?

• For 75%, it is best to find 25% and multiply this by 3.

Fill in the Blanks

What sum would we do to find 5%

Use / for to show divide.

What sum would we do to find 5%?

• For 5%, it is best to find 10% and divide it by 2.

• Alternatively you could get to 5% by dividing 100% by 20

Percentages without a calculator

• We are now going to calculate some percentages without using a calculator.

• We will find the percentages using the strategies we looked at in the previous section.

Percentages without a calculator

Multiple Choice

A post office deals with 800 customers in a day.

70% of these buy stomps.

How many customers buy stamps?

• 114

• 240

• 560

• 600

A post office deals with 800 customers in a day. 70% of these buy stomps.

How many customers buy stamps?

Multiple Choice

A shop usually sells a bottle of bath gel for £2.60

The shop has a special offer on bath gel.

How much is the discount on a bottle of bath gel?

• 13p

• 20p

• 26p

• 52p

A shop usually sells a bottle of bath gel for £2.60

The shop has a special offer on bath gel.

Fill in the Blanks

A woman is looking at her household bills throughout the year.

The total cost of electricity and supply for the fourth period is £120.

The electricity company adds VAT to this total at a rate of 5%

What is 5% of £120?

A woman is looking at her household bills throughout the year.

The total cost of electricity and supply for the fourth period is £120. 

The electricity company adds VAT to this total at a rate of 5% 

What is 5% of £120?

Fractions of an amount

Multiple Choice

Work out 60 ×  $$\frac{2}{3}$$  

• 90

• 20

• 40

• 45

Multiple Choice

Bob has £5, he donates 2/5 of it. How much does he have left?

• £1

• £2

• £3

• £4

Bob has £5, he donates 2/5 of it. How much does he have left?

Multiple Choice

Would you rather have...?

• 2/6 of £54

• 3/7 of £49

• 4/12 of £60

Would you rather have...?

Multiple Choice

Would you rather have...?

• 2/5 of £4

• 2/3 of £4.50

• 7/8 of £4

Would you rather have...?

Fill in the Blanks

In a shop the normal price of a jacket is £60
The cost of the jacket in a sale is $\frac{3}{4}$   of the normal price.
Work out  $\frac{3}{4}$   of £60

Fill in the Blanks

And some reasoning...
Which is greater... 18% of 200 or  $\frac{2}{5}\ of\ 80?$  

Exit ticket

Complete the Century task set for this week. You must do this to get your mark.